1. Field of the Invention
The present invention relates to an ion radiation damage prediction method, an ion radiation damage simulator, an ion radiation apparatus and an ion radiation method.
2. Description of the Related Art
Results of studies have indicated that it is quite within the bounds of possibility that damages caused by incoming ions generated in processing such as an etching process, a physical vapor deposition (PVD) process or an ion injection process to a fabricated film have a big effect on electrical characteristics of the device including the film. Such damages are thus a problem that needs to be solved as quickly as possible. A typical damage caused by incoming ions incident to a processed film serving as a target film of a process generating the ions is a crystalline defect. Thus, the target film including a pattern means a film hit by ions.
By merely making use of the contemporary measurement apparatus, however, it is difficult to conduct a direct analysis on a damage given to a real pattern (particularly, the side wall of the pattern). It is thus important to predict such a damage given to a film hit by incident ions by simulation in order to study details of relations between the damage and electrical characteristics of the device including the film as well as details of a measure that needs to be taken for improving the electrical characteristics.
For example, in a simulation of the existing ion implantation process or a stopping and range of ions in matter (SRIM) simulation, it is possible to predict the depth of penetration of incident ions into a target film which is assumed to have an amorphous structure. It is to be noted that for more information on the simulation of the existing ion implantation process, the reader is suggested to refer to documents such as Japanese Patent Laid-open No. Hei 7-115071 whereas for more information on the SRIM simulation, the reader is suggested to refer to documents such as “The stopping and Range of Ions in Solids,” J. F. Ziegler, J. P. Biersack and U. Littmark, Pergamon Press, New York, 1985.
However, a crystalline defect caused by the penetration of incident ions as a defect of the target film cannot be expressed quantitatively by taking the crystal structure of the target film into consideration. Typical examples of the crystalline defect are a disarray in the lattice crystal of the polysilicon and/or the silicon oxide.
In addition, a damage simulation process making use of the existing molecular dynamics simulator is carried out by considering interactions between incident ions penetrating a target film and atoms composing the target film. As a result, even in the case of a crystal-lattice disarray caused by energies of incoming ions, incidence angles of the incoming ions and the type of the target film can be predicted at an atomic level or a molecular level. It is to be noted that for more information on this simulation process, the reader is suggested to refer to documents such as H. Ohta and Hamaguchi, “Classical interatomic potentials for Si—O—F and Si—O—Cl systems,” Journal of Chemical Physics, Vol. 115, number 14, pp. 6679-6690, 2001.
Within a realistic time period of a computation that can be carried out by a computer such as one incorporated in an ordinary manufacturing apparatus, however, it is possible to compute only a distribution of damages in a very small limited area having typical dimensions of several nm×several nm. A typical example of the realistic time period of computation that can be carried out by a computer is several weeks. Due to limitations imposed by such a very small limited area, however, the actual computation carried out in accordance with molecular dynamics is applicable to cases not more than the case of an assumed planar target film which ignores created patterns. In addition, in the case of incoming ions each having a small mass (for example, hydrogen ion), the flying distance inside the target film increases. Thus, the time it takes to carry out the computation becomes even longer.
It is thus absolutely necessary to provide a new computation algorithm in which results of computation carried out to find a distribution of damages caused by radiation of ions in a real pattern having a scale of 100 nm and in an actual process of such a scale are fed back to the device process development within a short realistic time period such as several hours or several days. A distribution of damages is computed by for example predicting a distribution of crystalline defects and/or verifying a defect generation mechanism.
In addition, an ion radiation apparatus capable of correcting a process condition in order to reduce the number of damages by adopting the new computation algorithm described above becomes necessary for developments of high-performance of image sensors. Typical examples of the ion radiation apparatus are a dry etching apparatus and an ion injection apparatus.